Respiratory syncytial virus (RSV) infection is a significant cause of morbitity and mortality in infants and young children under the age of three. Hospitalized children with underlying heart and lung conditions are at severe risk. No vaccine is available at the present time, and available therapeutics have limited effectivness. This collaborative study utilized the rhesus RSV infection model to evaluate the antiviral efficacy of synthetic compound, ARB-96-417. A dose response experiment was conducted. Sixteen seronegative rhesus monkeys were divided into four groups. Three groups were treated intranasally with three dilutions of compound as a single prophyactic dose, two hours prior to intranasal RSV challenge. The fourth group was a water control group that, similarly, was challenged with RSV. All animals were followed for three weeks to monitor viral shedding in both the upper and lower respiratory tract, and the extent of the antiviral effect of the compound. Minimal reductions in virus titers occurred only in the nasal and lung lavage specimens in the monkeys receiving the highest doses of compound (10mg/ml), with lesser or negligible effects seen in the throat swab specimens or in the monkeys treated with the lower 2mg/ml or 0.4mg/ml doses. A short duration dose responsive reduction of virus shedding in the lungs of the high dose group was suggested. These results suggested also that this compound does have potential as an anti-RSV agent in vivo. Efficacy would be expected with a treatment regimen employing